This invention generally relates to audio transducers. More specifically, the invention pertains to improvements in the design of a transducer having one or more cylindrical or partially-cylindrical arcuate diaphragm and methods and apparatus for coupling the diaphragm to a voice coil driver system.
The prior art includes various audio transducers, some of which have a diaphragm that can generally be described as cylindrical in the broadest sense of the term. The cross-sectional profile need not be circular, but may be an open or closed polygon or curve. The cylindrical diaphragms may generally be formed from flat sheets that are curved so that all lines normal to the curved surface remain perpendicular to the longitudinal axis of the diaphragm. A variety of diaphragms of this type are disclosed in PCT Application International Publication No. WO93/23967. FIG. 1 is a top view of a prior art audio transducer having a pair of generally cylindrical diaphragms as described in the PCT application. FIG. 2 is a top view of another prior art audio transducer, having a pair of diaphragms with semi-circular cross sections in a numeral three arrangement. Additionally, various driver systems are known in the prior art, including voice coils and etched coils. FIG. 3 is a simplified perspective view of a transducer having a pair of cylindrical diaphragms and a double-sided etched coil driver system. In this arrangement, a coil is formed on a printed circuit type of substrate material and connected to adjacent portions of the two diaphragm lobes. This arrangement is shown in greater detail in FIG. 4, an enlarged, top view of a central portion of the transducer of FIG. 3, showing detail of the etched coil connected intermediate proximate edges of the diaphragms. Additional detail of transducers of this general type are disclosed in my prior U.S. Pat. No. 5,249,237.
While various prior art transducers are reasonable efficient, and provide relatively flat frequency response, there remains a need for additional improvements in the performance and cost of audio transducer systems. The present invention provides an improved audio transducer that can be manufactured at very low cost, while still providing excellent performance.